The present disclosure relates to a sheet feeder and to an image forming apparatus including the sheet feeder.
In an image forming apparatus, a sheet on which an image is to be formed is stored in a sheet feeding cassette of a sheet feeder. If the sheet absorbs moisture in a high humidity environment, there is a possibility of causing a defective image or jamming due to conveyance failure. Thus, there is an image forming apparatus provided with a dehumidifying heater arranged under the sheet feeding cassette.
However, because there are many gaps around the sheet feeding cassette, warm air generated from the dehumidifying heater may not be fully supplied to the sheet feeding cassette, causing such possibility that dehumidifying effect is exerted only on a vicinity of the dehumidifying heater or that the vicinity of the dehumidifying heater is locally heated and deformed.
Then, there is a sheet feeder provided with a sheet feeding cassette having a bottom face with a large number of vent holes to supply warm air into the sheet feeding cassette through the vent holes. There is also such a sheet feeder in which dehumidifying heaters are disposed corresponding to a peripheral of a sheet by considering a tendency that the sheet stored in the sheet feeding cassette has higher moisture content at a peripheral thereof more than a center thereof.
However, in the sheet feeder provided with the sheet feeding cassette having the bottom surface with the large number of vent holes, if a large size sheet is stored, the vent holes may be closed by the sheet and therefore enough ventilation cannot be assured. In the sheet feeder in which the dehumidifying heaters are disposed corresponding to the peripheral of the sheet, it is difficult to supply warm air to upper sheet feeding cassettes in a case where a plurality of sheet feeding cassettes is stacked.
Although it is also conceivable to provide a fan to supply warm air to the sheet feeding cassettes, it is desirable not to use the fan as much as possible to cut costs and to decrease noise.